
Marathon des Sables (Morocco) —
Taking place in the Moroccan Sahara Desert, the Marathon des Sables is a grueling six-day trek underneath the burning sun. The 254-kilometer race is one of the most unforgiving in the world.

Sand warriors —
Each competitor in the Marathon des Sables is responsible for carrying their own food, clothes and sleeping bags. The race, which started back in 1986, is run in temperatures that can reach nearly 50 C.

Arctic Circle Race (Greenland) —
It's 160 kilometers long and held in one of the world's harshest climates. The Arctic Circle Race sees competitors skiing through a snowy wilderness 65 kilometers north of the Arctic circle through temperatures as low as -30 C.

Cold comforts —
Hazardous weather conditions during the three-day Arctic Circle Race can get to competitors at night, with tents their only shelter from the cold.

Patagonia Expedition Race (Chile) —
Held in Chile, this trekking, cycling and kayaking challenge takes place in some of the most beautiful scenery on the planet.

Deep south —
The Patagonia Expedition Race is a 10-day event that takes place in the heart of southern Chilean Patagonia. The region's capital is the city of Punta Arenas, while the closest city to the race area will be Puerto Natales.

Four by four —
Patagonia Expedition teams must be mixed sex and made up of four people. The official race route is only released 24 hours before the start of the competition. The race takes between six and nine days to finish.

Iditarod Trail Invitational (Alaska) —
The Iditarod Trail Invitational ultra marathon takes place in February in Alaska, in one of the harshest climates on the planet.

Endless ice —
Iditarod Trail Invitational competitors can choose from a 350-mile (563-kilometer) run, ski or bike ride through the snow. For those that really want a challenge, there's the 1,000-mile (1,609-kilometer) route to Nome.

Jungle Marathon (Brazil) —
It's billed as the world's toughest jungle marathon. If the scorpions, snakes, caimans, piranhas and jaguars aren't enough, there's the 40 C temperatures and 99% humidity.
